Method of using a clot capture coil

ABSTRACT

A clot and foreign body removal device is described which comprises a catheter with at least one lumen. Located within the catheter is a clot capture coil that is connected to an insertion mandrel. In one embodiment, the clot capture coil is made out of a solid elastic or superelastic material which has shape memory, preferably nitinol. The elasticity or superelasticity of the coil allows it to be deformed within the catheter and to then reform its original coil configuration when the coil is moved outside of the catheter lumen. In another embodiment the coil is a biphasic coil which changes shape upon heating or passing an electric current. Once the coil configuration has been established, the coil can be used to ensnare and corkscrew a clot in a vessel. A clot is extracted from the vessel by moving the clot capture coil and catheter proximally until the clot can be removed or released into a different vessel that does not perfuse a critical organ. Foreign bodies are similarly captured by deploying the coil distal to the foreign body and moving the clot capture coil proximally until the foreign body is trapped within the coil. By removing the device from the body, the foreign material is also removed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 09/170,135, filed Oct.12, 1998, which is a continuation-in-part of U.S. patent applicationSer. No. 08/723,619, filed Oct. 2, 1996, now U.S. Pat. No. 5,895,398incorporated by reference herein, which claims priority to U.S.Provisional Patent Application Ser. Nos. 60/011,070, filed Feb. 2, 1996,and Ser. No. 60/018,715, filed May 31, 1996, each of which areincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to medical devices that are useful intreating thromboembolic disorders and for removal of foreign bodies inthe vascular system.

BACKGROUND OF THE INVENTION

Thromboembolic disorders, such as stroke, pulmonary embolism, peripheralthrombosis, atherosclerosis, and the like, affect many people. Thesedisorders are a major cause of morbidity and mortality in the UnitedStates.

Thromboembolic events are characterized by an occlusion of a bloodvessel. The occlusion is caused by a clot which is viscoelastic (jellylike) and is comprised of platelets, fibrinogen and other clottingproteins.

When an artery is occluded by a clot, tissue ischemia (lack of oxygenand nutrients) develops. The ischemia will progress to tissue infarction(cell death) if the occlusion persists. Infarction does not develop oris greatly limited if the flow of blood is reestablished rapidly.Failure to reestablish blood-flow can lead to the loss of limb, anginapectoris, myocardial infarction, stroke or even death.

Occlusion of the venous circulation by thrombi leads to blood stasiswhich can cause numerous problems. The majority of pulmonary embolismsare caused by emboli that originate in the peripheral venous system.Reestablishing blood flow and removal of the thrombus is highlydesirable.

There are many existing techniques employed to reestablish blood flow inan occluded vessel. One common surgical technique, an embolectomy,involves incising a blood vessel and introducing a balloon-tipped device(such as the Fogarty catheter) to the location of the occlusion. Theballoon is then inflated at a point beyond the clot and used totranslate the obstructing material back to the point of incision. Theobstructing material is then removed by the surgeon. While such surgicaltechniques have been useful, exposing a patient to surgery may betraumatic and best avoided when possible. Additionally, the use of aFogarty catheter is problematic because of the great risk of damagingthe interior lining of the vessel as the catheter is being withdrawn.

Percutaneous methods are also utilized for reestablishing blood flow. Acommon percutaneous technique is referred to as balloon angioplastywhere a balloon-tipped catheter is introduced to a blood vessel,typically through an introducing catheter. The balloon-tipped catheteris then advanced to the point of the occlusion and inflated in order todilate the stenosis. Balloon angioplasty is appropriate for treatingvessel stenosis but is not effective for treating acutethromboembolisms.

Another percutaneous technique is to place a microcatheter near the clotand infuse streptokinase, urokinase or other thrombolytic agents todissolve the clot. Unfortunately, thrombolysis typically takes hours todays to be successful. Additionally, thrombolytic agents can causesevere hemorrhage and in many patients the agents cannot be used at all.

U.S. Pat. Nos. 4,706,671 and 5,011,488 both describe the use of a coiledsection for the removal of thromboembolic material. However, neitherpatent describes a device that is marketed. U.S. Pat. No. 4,706,671teaches the use of a hollow flexible elastomeric material to form theshape of the coiled section. The coiled section is hollow to allow forthe insertion of a liquid into the hollow center such that the coilsbecome stiff. U.S. Pat. No. 5,011,488 teaches the use of a coiledsection that is fixed on both the proximal and distal ends such that theoperator of the device can change the shape and size of the coils.However, this device may be impossible to manufacture and is impossibleto use in small vessels.

Another problematic area is the removal of foreign bodies. Foreignbodies introduced into the circulation can be fragments of catheters,pace-maker electrodes, guide wires, and erroneously placed embolicmaterial such as thrombogenic coils. The only available retrievaldevices for the removal of foreign bodies are devices which form a loopthat can ensnare the foreign material by decreasing the size of thediameter of the loop around the foreign body. The use of such removaldevices is difficult and sometimes unsuccessful.

Thus, there exists a need for the development of a device that can beeasily deployed into the circulatory system for the removal ofviscoelastic clots and foreign bodies. There is also a need for a devicewhich could be used as a temporary arterial or venous filter to captureand remove thromboemboli formed during endovascular procedures.

SUMMARY OF THE INVENTION

The present invention is a coil type device that is useful in removingclots and foreign bodies in vessels. The invention comprises a catheterwith. at least one lumen. Located within the catheter is a clot capturecoil that is connected to an insertion mandrel. The clot capture coil ismade out of a solid elastic or superelastic material which has shapememory. The elasticity or superelasticity of the coil allows it to bedeformed within the catheter and then to reform its original coilconfiguration when the coil is moved outside of the catheter lumen.

In an alternate embodiment, the coil is made out of a biphasic materialwhich changes shape upon heating or the passage of electrical current.The coil is straight initially, and then after passing electricalcurrent or heat the coil changes to its coil configuration.

Once the coil configuration has been established, the coil can be usedto ensnare and corkscrew a clot in a vessel. The clot is extracted fromthe vessel by moving the clot capture coil and catheter proximally untilthe clot can be removed or released into a different vessel that doesnot perfuse a critical organ. The coil can also be used as a temporaryarterial or venous filter to capture and remove thromboemboli formedduring endovascular procedures. Foreign bodies are captured by deployingthe coil distal to the foreign body and moving the clot capture coilproximally until the foreign body is trapped within the coil. Byremoving the device from the body, the foreign material is also removed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to thefollowing drawings wherein:

FIG. 1a is a schematic illustration of an occluded artery with amicrocatheter and the clot capture coil of the present invention;

FIG. 1b is a schematic illustration of an occluded artery with amicrocatheter and a clot capture coil inserted through an occlusion;

FIG. 1c is a schematic illustration of the deployment of the clotcapture coil within an occluded artery;

FIG. 1d is a schematic illustration of the clot capture coil of thepresent invention encountering a clot in an occluded artery;

FIG. 1e is a schematic illustration of the clot capture coil ensnaringthe clot in an occluded artery;

FIG. 1f is a schematic illustration of the clot of FIG. 1e being movedwithin an occluded artery via the clot capture coil;

FIG. 1g is a cross section of the artery and the catheter of FIG. 1ealong line 1 g—1 g.

FIG. 2a is a schematic illustration of an occluded artery and analternate embodiment of the clot capture coil;

FIG. 2b is a schematic illustration of a microcatheter passed through aclot within an occluded artery and the extended coil of the clot capturecoil within the catheter;

FIG. 2c is a schematic illustration of the deployment of the clotcapture coil in an occluded artery;

FIG. 2d is a schematic illustration of a clot capture coil ensnaring aclot within an occluded artery;

FIG. 2e is a schematic illustration of the removal of a clot via a clotcapture coil illustrating the corkscrewing and ensnaring effect of thecoil within the viscoelastic clot;

FIG. 2f is a cross section of the artery and catheter of FIG. 2d at line2 f—2 f.

FIG. 3 is an alternate coil configuration;

FIG. 4 is an alternate coil configuration;

FIG. 5 is a further coil configuration;

FIG. 6 is an additional coil configuration;

FIG. 7 is a further coil configuration;

FIG. 8 is a double helix coil configuration and a single lumen catheter;

FIG. 9 is a double helix coil configuration and a double lumen catheter;

FIG. 10a is a schematic illustration of the clot capture coil and anintroducer;

FIG. 10b is a schematic illustration of a clot capture coil straightenedwithin the inner lumen of the introducer of FIG. 10a;

FIG. 11 is a plan view of the present invention being deployed within anintroducing catheter with a side suction port;

FIG. 12 is a schematic view of the present invention being deployedwithin an introducing catheter such that the coil section is within theinferior vena cava of a patient; FIG. 13 is an alternate coilconfiguration that is particularly useful for removing clots in asurgically created arteriovenous fistula of a hemodialysis patient;

FIG. 14 is a further coil configuration; and

FIG. 15 is another coil configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to FIGS. 1a-1 g, a clot capture coil device 10 is generallyillustrated within an artery 20 with a clot 22. The device comprises acatheter 12 with at least one lumen 14, a clot capture coil 18, and aninsertion mandrel 16.

The catheter 12 can be any commercially available catheter that is madeout of any appropriate biologically compatible material. Typically, thecatheter will have a single lumen 14 and is constructed out of aflexible elastomeric materials such as silicone, rubber,polyvinylchloride, polyurethanes, polyesters, polytetrafluoroethylene,and the like. The catheter has to be flexible enough and long enough tonavigate through blood vessels to the occluded vessel 20 where clot 22is located. Typically the catheter will range in length from about 20 toabout 175 .

The outer diameter of the catheter can also vary. Typically the outerdiameter will range from about 2 to about 10 French (one French=0.013inch). The inner diameter will range from about 1 to about 9 French.

The insertion mandrel 16 has to be relatively stiff to support the coil18. In the preferred embodiment, the insertion mandrel is made out ofstainless steel and is a solid wire of from about 0.006 to about 0.038inch in diameter. Other materials could be used such as a hard plastic,nitinol, and the like to make the insertion mandrel. The insertionmandrel is 10 to 20 cm longer than the catheter such that the operatorof the device (typically a physician) can control the insertion mandrelby gripping the proximal end which extends from the proximal end of thecatheter.

Connected to the insertion mandrel is the clot capture coil 18. In oneembodiment, the coil is made from a flexible solid elastic orsuperelastic material which has shape memory, i.e., it can deform to astraight position and then return to a resting coil configuration. In apreferred embodiment, the coil is made out of a solid nitinol wire witha diameter of about 0.001 to about 0.038 inch. The use of nitinol inmedical devices is well known in the art. Nitinol is preferred becauseof its superelasticity and its shape memory. However, other solidmaterials that are also elastic or superelastic and have shape memorycould also be used such as some synthetic plastics, metallic alloys, andthe like. To make the coil, the nitinol wire is wrapped around a mandrelinto the coil configuration. The nitinol is then heated to anappropriate temperature such that the nitinol wire adopts the coilconfiguration as its resting shape upon cooling. The diameter of thecoils can vary depending on the size of the vessel occluded. Thediameter can range from about 1 mm for small vessels to about 30 mm forlarge vessels such as the pulmonary arteries or inferior vena cava. Thelength of the coil can also vary but typically ranges from about 3 toabout 100 mm in the proximal to distal direction. Because the nitinolcoil is superelastic, the coil can be extended to a completely straightconfiguration with the use of minimal force and then reform to itsnatural resting configuration when the force is removed. In use, thecoil is extended by using the insertion mandrel to insert the coil andthe mandrel into the narrow lumen of the catheter.

In another embodiment, the coil is made out of a solid biphasic materialwhich changes shape upon heating or the passage of electric current. Apresently preferred material is biphasic nitinol which has a straightconfiguration initially, and changes to a coiled configuration upon thepassage of electric current or heating. The use of biphasic nitinol iswell known in the medical arts for other purposes. The biphasic nitinolcoil would be made using ordinary skill in the art such that the nitinolcoil is straight initially and then forms the appropriate coilconfiguration. As would be apparent to a person skilled in the art, thebiphasic coil could also be constructed such that the initial coilconfiguration is the normal shape and that the biphasic coil straightensupon passing electric current or heating. The coil dimensions would besimilar to the dimension detailed above for the shape memory coil.

The coil section of either the shape memory coil or the biphasic coilcan have many different configurations. Similar reference numerals areused throughout the figures to indicate similar components of theembodiments. In the embodiment illustrated in FIGS. 1a-1 f, the coil isbarrel-shaped such that the diameter of the coil is relatively small atthe distal and proximal ends of the coil and is relatively large in thecenter of the coil. In a typical coil configuration, the diameter of thecoil ranges from 2 mm at the proximal and distal ends and expands to 10mm in the center. However, other sizes are also useful depending on therelative size of the occluded vessel. At the proximal end of the coil isa small circular loop 26. In the preferred illustrated embodiment, thecircular loop is placed around the mandrel and is freely slidable overthe mandrel. The distal end of the barrel-shaped coil is permanentlyconnected to the distal end 24 of the insertion mandrel. Thus, in thisembodiment the coil extends proximally from the distal end of theinsertion mandrel. In the preferred embodiment the coil is welded ontothe distal end of the insertion mandrel. Other means of permanentlyconnecting the coil could also be used such as crimping the coil, gluingthe coil, screwing the coil into a screw type mount, and the like.

A different coil configuration is illustrated in FIGS. 2a-2 f. In thisembodiment, the coil 30 is connected at its proximal end to the distalend 24 of the insertion mandrel 16. Thus, the coil extends distally fromthe distal end of the insertion mandrel. The distal end 32 of the coilis free floating. The coil is conically shaped with the diameter of thecoils decreasing distally to the free end 32. Embodiments where the coilis connected to the proximal end are preferred for use in removing clotsfrom small and/or tortuous vessels as will be discussed below.

The size and shape of the coils can vary and different representativeembodiments are illustrated in the different figures. FIG. 3 illustratesan alternate embodiment where the coil 34 is attached at its proximalend to the distal end of the insertion mandrel 16. Thus, the coilextends distally away from the distal end of the insertion mandrel. Thecoil is shaped like an inverted cone with the diameter of the coilsincreasing distally. This embodiment is particularly useful forretrieving clots from small (1-2 mm diameter) vessels in the cerebraland coronary circulations. The diameter of the coils in thisconfiguration are typically from about 1 mm to about 3 mm, could belarger depending on the relative size of the occluded vessel.

FIG. 4 illustrates a cone-shaped coil 36 where the distal end of thecoil is connected to the distal end of the insertion mandrel. FIG. 5 isa similar embodiment to FIG. 4 except that the coil 38 is wound tightersuch that there are more revolutions per inch. In both FIGS. 4 and 5 thecoil section extends proximally from the distal end of the insertionmandrel.

FIG. 6 illustrates a different embodiment where the proximal end of thecoil 42 is connected to the insertion mandrel's distal end. The coil isshaped like an inverted cup which has a constant diameter until the coilreaches its most distal end where the diameter decreases.

FIG. 7 is a similar embodiment to FIGS. 1a-1 f except that thebarrel-shaped. coil 40 is connected to the distal end of the insertionmandrel such that the coil extends distally instead of proximally.

The embodiment of FIG. 8 is a double helix coil configuration that isuseful for large clot removal. The configuration is such that onecontinuous piece of wire is used to form the double helix configuration.Both ends of the coil 44 and 46 are connected to the distal end of theinsertion mandrel 16. In the preferred embodiment, both ends are weldedonto the insertion mandrel 16 at weld lines 45 and 47. The coil has beenheat treated such that it forms a resting double helix shape. The twohelixes 48 and 50 intertwine and are connected at the top of each helixat point 52. When the double helix coil is withdrawn into the singlelumen catheter by translating the insertion mandrel, the helixesstraighten until the coils are completely withdrawn into the catheter'slumen. By translating the insertion member. in the opposite direction,the coil is forced out of the lumen of the catheter and then reforms thedouble helix configuration.

FIG. 9 is an alternate double helix embodiment where the double helix isused in conjunction with a double lumen catheter 56. The lumens 58 and60 each receive an insertion mandrel 16 and 16′. Each insertion mandrelin turn is permanently connected to one of the ends of the coil. At theproximal end of the insertion mandrels are optional connecting bars 17which keep the relative spacial relationship of each insertion mandrelconstant. In this embodiment, as the helixes are withdrawn into thecatheter, each one straightens out and is kept separate within therespective lumens. When the helixes are then deployed by translating theinsertion mandrel, the helixes reform the double helix configuration.The optional connecting bars 17 are used to ensure that each helix isbeing deployed by the translation of the insertion mandrels and are inunison with each other such that the double helix configuration isalways obtained upon full deployment.

FIG. 13 illustrates a long coil 140, ranging from about 2 cm to about 10cm that is especially useful for removing clots in a surgically createdarteriovenous fistula of a hemodialysis patient. The coil could also beused for removing long clots in the venous system and long clots in asurgically created by-pass graft. The arteriovenous fistulas arenormally surgically created on the forearm of a hemodialysis patient andallows for easy access to the blood stream for hemodialysis treatment.Unfortunately, these fistulas often become clogged with long blood clotsand have to be surgically repaired or a new fistula created. The longclot capture coil 140 is connected to the insertion mandrel 16 at thecoil's proximal end.

FIGS. 14 and 15 illustrate two further coil configurations. FIG. 14 is acylindrical coil 150 attached to the distal end of the insertion mandrel16. FIG. 15 is a random tangle coil attached to the insertion mandrel16. The random tangle is manufactured by extruding the coil material ina random fashion. The random tangles made by such a process would varyeach time the tangles are manufactured, and thus, the random tanglepictured in FIG. 15 is for illustration only.

In a preferred embodiment, part or all of the coil is either made of, orcovered by, a radiopaque material to permit monitoring of the locationof the coil using x-rays. In a particularly preferred embodiment, thedistal tip of the coil is radiopaque. The coil can be made, for example,of gold or platinum, or anther radiopaque material. If the coil is madefrom nitinol, which is not radiopaque, the nitinol coil can be modifiedto make part or all of it radiopaque. For example, a microcoil ofplatinum, gold or other radiopaque material can be coiled around thedistal tip of the nitinol coil. The radiopaque microcoil canalternatively be wrapped around any other part of the nitinol coil, oreven around the entire coil.

FIGS. 10a and 10 b illustrate the use of an introducer 72 with lumen 74.The introducer is a relatively long (170 cm long) single lumen catheterthat is used to straighten the coil section of a shape memory coil whichextends distally, such as the coils in FIGS. 2, 3, 6, and 7, prior toinsertion into the catheter 12 of the present invention. A longerintroducer would be used for the arteriovenous fistula coil of FIG. 13.The insertion mandrel is inserted into the introducer in a retrogradedirection (indicated by the arrow in FIG. 10a). Once the introducerreaches the shape memory coil section, the coil section straightens outalmost to a complete straight line. In a coil section that extendsdistally outward, the inner diameter of the introducer and the catheterare sized to be just slightly larger than the diameter of the insertionmandrel and the coil section. That is, if the insertion mandrel and thecoil are each made from 0.008 inch diameter wires, then the innerdiameter of the introducer is preferably 1 to 2 French. Once the coilhas been straightened out completely, the coil within the introducer isaligned with the catheter and then advanced in an anterograde directioninto the catheter.

The above detailed description describes some of the numerousembodiments of the present invention. Below is a discussion of some ofthe numerous uses of the invention.

In use, a patient presenting symptoms of a thromboembolic disorder isexamined radiographically using angiography to locate an occlusion andto confirm the diagnosis. A large introducing catheter 130 (see FIG. 12)is then inserted into an appropriate vessel (usually the femoral arteryor the femoral vein). A small catheter or microcatheter 12 is thenintroduced into the vessel via the introducing catheter and advancedusing a guide wire or the like into the occluded vessel. The catheter 12is then passed through the viscoelastic clot. Once the catheter is inplace and through the viscoelastic clot the clot capture coil isintroduced into the catheter using the insertion mandrel and advanced tothe distal tip of the catheter. For the shape memory clot capture coilsthat extend proximally from the insertion mandrel (as in FIGS. 1a-1 f,the coil and the insertion mandrel are inserted directly into theproximal end of the catheter and advanced to the distal end (see FIG.1b). For the shape memory clot capture coils that extend distally fromthe insertion mandrel (as in FIGS. 2a-2 e), the introducer of FIGS. 10aand 10 b is used as described above. For the biphasic coils, the coilsare introduced in the straight configuration by either having thestraight configuration the natural configuration or by straightening anatural coil configuration by passing electric current or heating thecoil.

Once the catheter and the clot capture coil have transversed the clot,the insertion mandrel is translated distally relative to the catheter.With a shape memory coil, the coil deploys and reforms its naturalconfiguration outside the distal end of the catheter. By comparing FIGS.1c and 2 c it is apparent that the shape memory coils which extenddistally from the insertion mandrel immediately start to form the coilconfiguration once part of the coil is freed from the confines of thelumen of the catheter. These embodiments are particularly useful forclot removal in vessels that are small and/or tortuous where there isnot much room for the advancement of the insertion mandrel and the coil.In the embodiments where the shape memory coil extends proximally fromthe distal end of the insertion mandrel, the entire length of the coilneeds to be freed from the confines of the lumen of the catheter beforeit reforms the coil configuration. These embodiments are useful for theremoval of large clots in large vessels because the coil is bettersupported and the coils can collapse upon each other. For example, asillustrated in FIGS. 1c-1 f the proximal end of the coil which is aslidable loop 26 mounted around the insertion mandrel will encounter theclot material first. The slidable loop then slides distally until thecoils form a double inverted cone-shaped configuration. The coils willoverlap and thus give more support for the removal of large clots.

The biphasic coils are deployed similarly except that electric currentor heat is used to form the coil configurations if the straightconfiguration is the natural shape. If the coil configuration is thenatural shape, then the user stops applying electric current or heat andthe coil configuration will reform.

The clot is then retrieved by translating the insertion mandrel alongwith the catheter proximally. When the clot capture coil is pulledproximally the clot becomes ensnared. Additionally, while pullingproximally on the insertion mandrel, the coil is rotated by rotating theinsertion mandrel to transfix the clot by corkscrewing the clot into thecoils. The viscoelastic properties of the clot allow the clot to becaptured within the side coils and to be pulled down using the mostdistal coils as a capture cup. The clot can then be completely removedor released into a vessel that does not perfuse a critical organ such asan external carotid artery.

A particularly useful introducing catheter is illustrated in FIG. 11.The introducing catheter 110 is hollow with a single lumen and has a Yjunction towards its proximal end. The introducing catheter is astandard commercially available introducing catheter. The introducingcatheter has two ports, 112 and 114. Port 112 is in straightcommunication with the longitudinal axis of the introducing catheter andis useful for is the insertion of the catheter 12, coil 30 and insertionmandrel 16 of the present invention. The other port, which is angledaway form the longitudinal axis of the insertion catheter, is for theattachment to a suction line from a vacuum source. Located at the distalend 116 of the introducing catheter is a marker band 118 that can belocated via radiographic means while the introducing catheter is beingused.

In practice, the introducing catheter 110 is inserted through a largevessel and through the vascular system to a position near a clot in anoccluded artery under fluoroscopic guidance. The catheter 12, is theninserted through port 112 and through the introducing catheter such thatthe distal end of the catheter 12 has passed the distal end 116 of theintroducing catheter. The catheter 12 is then translated across theclot. The coil 30 and insertion mandrel 16 are then inserted into thecatheter 12. The insertion mandrel is then translated through thecatheter 12 until the coil 30 is deployed in the vessel. The insertionmandrel is then translated proximally to ensnare the clot within thecoil and then the catheter, coil and clot are translated toward thedistal end 116 of the introducing catheter 110. Once the clot and thecoil are at the distal end 116, suction is applied via port 114 to suckpart of the clot into the distal end 116. The suction helps to keep theclot within the coil. Then the introducing catheter 110, the catheter12, the clot and the coil 30 are removed from the patient.

FIG. 12 illustrates the invention being used as a filter in the inferiorvena cava of a patient with a venous thrombus in a lower limb. Acommercially available introducing catheter 130 is advanced into afemoral vein 122 and into the inferior vena cava 128 below the heart126. A catheter 12 is then advanced through the introducing catheter.The-coil 120 and insertion mandrel 16 are then advanced through thecatheter 12 and the coil 120 is deployed within the inferior vena cava.The coil 120 has a large diameter, around 20 mm to 30 mm, such that whendeployed it fits snugly within the inferior vena cava. The coil acts asa filter wherein pieces of the thrombus become trapped in the coilinstead of being transported to the lungs. The thrombic material canthen be removed from the patient.

Foreign bodies are removed as described above except that the foreignbody becomes ensnared in the clot capture coil instead of a clot. Due tothe numerous coils, it is much easier to ensnare a foreign body thanusing a loop type device.

The following examples illustrate some of the uses of the invention. Theexamples are provided for illustration purposes and are not meant tolimit the invention to the specific examples.

EXAMPLE 1

The clot capture coil was clinically tested in pigs. In the first studya pig's femoral artery was isolated and a large commercially availableintroducing catheter was inserted into the femoral artery. Arterialblood was then withdrawn and allowed to clot in vitro.

An arterial catheter was then inserted through the introducing catheterand into the carotid artery. The coagulated arterial blood was thenreleased into the carotid artery branches via the arterial catheterresulting in the formation of numerous emboli.

Angiography was used to locate the emboli. While preforming angiographya microcatheter (outer diameter of 3 French and inner diameter of 1French) was inserted into an occluded carotid artery using a guide wirefor placement and standard microcatheter placement techniques. Themicrocatheter was advanced distally past the clot. The guide wire wasthen withdrawn from the microcatheter.

A shape memory clot capture coil connected to an insertion mandrel wasthen introduced into the microcatheter using a small introducer. Thecoil configuration was the type illustrated in FIG. 2a. Because the coilextends distally from the insertion mandrel a small introducing catheterhad to be used to introduce the clot capture coil into themicrocatheter. The insertion mandrel and the clot capture coil wasinserted in a retrograde direction into the introducing catheter. Theinner diameter of the introducing catheter was identical to themicrocatheter. The clot capture coil became straight due to thesuperelastic properties of the coil and the small inner diameter of theintroducer. Once the coil was completely within the introducer, theintroducer was aligned with the microcatheter and the coil was insertedinto the microcatheter in an anterograde direction.

The clot capture coil was slowly advanced to the distal end of themicrocatheter by translating the insertion mandrel. As the insertion.mandrel was advanced, the coil began to be expressed from the distal endof the microcatheter. As more and more of the coil was expressed, thecoil deployed and returned to its natural resting coiled shape as inFIG. 2c.

The clot capture coil was then pulled proximally to ensnare the clot.While pulling proximally, the coil was rotated by rotating the insertionmandrel to transfix the clot by corkscrewing the clot into the coils.The clot was then completely removed from the pig by removing themicrocatheter, insertion mandrel, and the clot within the clot capturecoil from the pig's femoral artery. EXAMPLE 2

The procedure of Example 1 was repeated using the shape memory clotcapture coil configuration illustrated in FIG. 3. The clot wassuccessfully corkscrewed and ensnared and removed from the pig'soccluded cerebral artery. EXAMPLE 3

The procedure of Example 1 was repeated using a shape memory clotcapture coil as illustrated in FIG. 4. Because this embodiment has thecoil extending proximally from the distal end of the insertion mandrel,the clot capture coil was directly inserted into the microcatheterwithout the use of a small introducer. A clot in an occluded carotidartery was ensnared in the coil and completely removed.

Thus, a clot capture coil is disclosed which allows for the removal ofthromboembolic material and foreign bodies from a blood vessel. Whileembodiments and applications of this invention have been shown anddescribed, it would be apparent to those skilled in the art that manymore modifications are possible without departing from the inventiveconcepts herein. The invention, therefore, is not to be restrictedexcept in the spirit of the appended claims.

What is claimed is:
 1. A method of removing an obstruction in a bloodvessel comprising: advancing a catheter through an obstruction, thecatheter having a lumen; positioning an obstruction retriever within thelumen of the catheter, the obstruction retriever having an obstructionengaging portion extending from an insertion element, the obstructionengaging portion having a first coiled section and a second coiledsection, a distal end of the second coiled section being attached to thefirst coiled section, the obstruction engaging portion being movablebetween a collapsed position and an expanded position and being in thecollapsed position when positioned in the lumen and being naturallybiased toward the expanded position when positioned outside the lumen;moving the obstruction engaging portion into engagement with theobstruction; and removing the obstruction.
 2. The method of claim 1,wherein the positioning step is carried out with the distal end of thesecond coiled section being attached to a distal end of the first coiledsection.
 3. The method of claim 1, wherein the positioning step iscarried out with the second coiled section having a proximal end whichis also attached to the first coiled section.
 4. The method of claim 1,wherein the positioning step is carried out with the first and secondcoiled sections including a common, integrally formed element.
 5. Themethod of claim 1, wherein the positioning step is carried out with thesecond coiled section having proximal and distal ends coupled to theobstruction engaging portion.
 6. The method of claim 1, wherein thepositioning step is carried out with the first and second coiledsections forming a double helix shape.
 7. The method of claim 1, whereinthe positioning step is carried out with the first and second sectionsbeing intertwined.
 8. The method of claim 1, wherein the positioningstep is carried out with the first and second sections being coupled toa common insertion mandrel so that the first and second coiled sectionsare manipulated at the same time.
 9. The method of claim 1, wherein thepositioning step is carried out with the insertion element including afirst element coupled to the first coiled section and a second elementcoupled to the second coiled section so that the first and second coiledsections may be manipulated independently with the first and secondelements.
 10. The method of claim 1 wherein the obstruction engagingportion is made of a superelastic material.
 11. The method of claim 1further comprising introducing the catheter through a second catheter tothe obstruction.
 12. The method of claim 11 further comprising: loadingthe obstruction retriever into the catheter in a retrograde direction;and thereafter introducing the catheter through the second catheter. 13.The method of claim 1 wherein the obstruction engaging element has agenerally conical shape.
 14. The method of claim 1 wherein the catheterhas only one lumen.
 15. The method of claim 1 wherein the moving step iscarried out by moving the obstruction engaging portion proximally intoengagement with the obstruction.
 16. The method of claim 1 wherein themoving step is carried out by rotating the obstruction engaging portion.17. The method of claim 1 wherein the first and second coiled sectionsare wound in same direction.